Which of the following is NOT a primary component of a dive computer?

A dive computer typically includes several key components that assist divers in monitoring their underwater environment and ensuring safety during dives. The primary components include a depth gauge, which measures the current depth and helps divers monitor their ascent and descent rates to prevent decompression sickness. A timer is also essential, as it tracks the duration of the dive, allowing divers to manage their bottom time based on their planned limits. Additionally, a nitrogen loading calculator is a critical function, helping divers keep track of the amount of dissolved nitrogen in their bodies based on their depth and time underwater, which is crucial for avoiding decompression sickness.

In contrast, a breathing rate monitor, while useful for certain scenarios and enhancing a diver’s situational awareness, is not a fundamental component of a dive computer. Most dive computers focus on depth, time, and nitrogen loading calculations rather than tracking a diver's breathing rate, which is typically assessed through other means or equipment. Therefore, the correct answer highlights that the breathing rate monitor is not a primary component of a dive computer.